The present relation relates to lightning suppression attenuators. More particularly, the present invention relates to devices for reducing the magnitude of current of the lightning current wavefront as it moves outwardly from a lightning strike. More particularly, the present invention relates to devices for protecting the electrical systems and critical load systems of facilities adjacent to a tower.
Lightning conceivably may have provided humankind with a first source of fire, but lightning has otherwise been a destructive force throughout human history. Strategies and apparatus for reducing the likelihood of damage by lightning are fairly old, including, for instance, lightning rods that have been use for approximately 200 years. While the use of such rods and other precautionary steps and safety devices reduce the damage and injury that would otherwise result from lightning today, it remains an enormously dangerous natural phenomenon that claims hundreds of lives worldwide every year and destroys a substantial amount of property. Somewhat paradoxically, advances in other areas of technology have increased, rather than diminished, the damaged caused by lightning. This is because relatively low voltage and current levels can damage integrated circuits and other modem electronic components, with the result that many electronic devices are more susceptible to lightning damage today than ever before. Many devices to which microprocessors technology has been added are more susceptible to lightning damage as a result of such improvements. Additionally, lightning is capable of inducing substantial currents not only in electrical circuits directly struck by it but also in circuits located within the magnetic field induced by a nearby lightning strikes, giving each strike enormous destructive potential.
One of the most common areas of lightning strikes are large telecommunications and camera towers that extend upwardly from the earth. Typically, such towers include an electronic device at the top which serves to transmit or receive information. Since lightning will follow a path of least resistance on its way to the earth, the towers are very attractive to lightning. It is well known that lightning is particularly attracted to areas of positive ions and is repelled by areas of negative ions. Since the electronic devices at the top of towers often operate on AC power, an attractive source of positive ions is generated at the top of the tower.
Whenever lightning strikes a tower, an enormous amount of damage is created. Typically, the electronic device at the top of the tower is completely destroyed by the lightning. Furthermore, the structure of the tower and other associated electronics at the top of the tower can become damaged. Repair efforts on the tower are often time consuming and expensive. Typically, complete replacement of the electronic device at the top of the tower is required. As such, it is very important to develop a device which resists or prevents lightning strikes.
A major problem associated with such lightning strikes, even upon towers which employ extensive lightning suppression and grounding systems is that, when the lightning passes to the earth, a wavefront of current will pass outwardly from the tower through the earth. If this wavefront of lightning current through the earth is not suppressed, then it can be damaging to the facility adjacent to the tower or to the critical load systems within the facility. If the ground transference of lightning current should connect with the critical load system for the facility, then a great deal of damage can occur to the computer systems within the building. Similarly, if the lightning current wavefront should encounter the electrical system for the building, then damage can occur to items connected to the electrical system.
It is an object of the present invention to provide a lightning suppression attenuator that effectively prevents lightning strikes from affecting the building service connections and the critical load systems for facilities adjacent to the lightning strike.
It is another object of the present invention to provide a lightning suppression attenuator that effectively minimizes the magnitude of the lightning current as it moves radially outwardly from the lightning strike.
It is a further object of the present invention to provide a lightning suppression attenuator which will minimize the damaging effects of lightning.
It is a further object of the present invention to provide a lightning suppression attenuator which is easy to install, relatively inexpensive and easy to manufacture.
It is a further object of the present invention to provide a lightning suppression system which effectively employs an arrangement of grounding rods for minimizing lightning effects.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a lightning suppression attenuator that comprises an enclosure with a coil of conductive wire received within the interior volume of the enclosure. The coil has a first lead extending outwardly of the enclosure and a second lead extending outwardly of the enclosure. A conductive grit fills the interior of the enclosure. The first lead is connected to a first discharge grounding system. The second lead is connected to a second discharge grounding system.
In the present invention, the conductive grit comprises a first layer of conductive grit residing across a bottom of the enclosure. The coil is positioned on the top of this first layer of conductive grit. A second layer of conductive grit extends over and around the coil within the enclosure. A rigid foam material is injected through holes formed on the walls of the enclosure so as to extend around the conductive grit and over the coil. The coil has a central void with turns of wire extending around the central void. In the preferred embodiment of the present invention, the wire is AWG#2 600 volt insulated copper wire. The coil, preferably, will have approximately fifteen turns of wire around the central void. The first lead is in liquid-tight sealing relationship with a first opening formed on the enclosure. The second lead is in liquid-tight sealing relationship with a second opening formed in the enclosure.
The present invention is also a lightning suppression system comprising a first grounding system installed in the earth, a first lightning suppression attenuator having a first lead electrically connected to the first grounding system, and a second grounding system installed in the earth. The lightning suppression attenuator has a second lead electrically connected to the second grounding system. The lightning suppression attenuator has a configuration described herein previously.
The first grounding system can be a tower that has a grounding rod extending into the earth. The second grounding system can be a building service electrical system having a grounding rod extending into the earth. The lightning suppression attenuator is interposed between the tower and the building service electrical system. A third grounding system is installed in the earth. A second lightning suppression attenuator has a first lead electrically connected to the second grounding system and a second lead electrically connected to the third grounding system. In the preferred embodiment of the present invention, the third grounding system can be a critical load system.
The first lightning suppression attenuator and the second lightning suppression attenuator each include a first grounding rod connected to the first lead and installed in the earth and a second grounding rod connected to the second lead and installed in the earth. The first grounding system includes a first grounding rod, a second grounding rod, and a third grounding rod electrically connected together in a geometrical pattern. Each of these grounding rods includes a central shaft and a plurality of vanes extending radially outwardly from the central shaft. The central shaft and the plurality of vanes are of a conductive material.